Support nerd fonts

1. [Feature] Use nerd-icons instead of all-the-icons.
2. [Feature] Support mu4e-modeline-mode.
3. Compatible with flychecker-color-mode-line.
4. feat: support treesit (xx-ts-mode).
5. feat: backport align-right feature from 30.
6. [Feature] Add eldoc segment.
7. feat: align right hand side of active mode line with variable-pitch font .
8. Bug fixes and improvements.